Shots 2 and 4 capture the essence of a mud run pretty well. Shots 1 and 3 lack the simplicity and clear, obvious center of interest that make photos 2 and 4 strong. LIke on the first photo, there's runner 475 coming up, the woman falling down, the guy standing, and the guy who's about to fall on his keister...four people, and all those V-shaped Valeri flags make it difficult to really feast on any solid detail--it serves as an overview of the event, but it's kind of a "busy" view of the event. Shot #3 does little for me, but I think #4 is simple, clear, and carries a LOT of feeling with it.

THIS kind of event is a prime example of the type of event where a lens protective filter might make 100% sense. That and motocross and dirt track races.